The invention relates to a cutting tool for separating and/or formatting sheet material such as plastic material sheets, light metal sheets, wood sheets and the like, with a rotationally drivable support body on whose circumference a plurality of cutting teeth with a cutting edge arranged on the tooth profile is provided, wherein the cutting teeth have a radially outwardly positioned front-cutting area in which a separating cutting edge is formed and are provided with main cutting edges in a formatting area determining the cutting width of the tool.
Known cutting tools are comprised of a rotationally driven support body on whose circumference a plurality of cutting teeth having a cutting edge formed on the tooth profile are arranged. When cutting and formatting plastic materials, light metals, cement fiber sheets, wood and wood-based materials with a coating or the like, smooth cut surfaces and cut edges free of tearing are required. During cutting, the workpiece is separated wherein a separating cut is performed in the sheet material with the tool such as, for example, a circular saw blade. During formatting the cut-off part is comminuted in order to then remove it by means of a suction device. For this purpose, a chipping tool is conventionally used which produces a cut surface on the workpiece.
Available on the market are substantially two chipping tool designs. In a compact chipping tool a cutting row with many teeth is arranged on a support body for separating and adjacent thereto one or more cutting rows with a low number of teeth are provided for comminuting. The other design is a saw chipping tool in which only cutting rows with a low number of teeth are arranged on the support body. A tool with a cutting row having a high number of teeth, for example, in the form of a circular saw blade, is provided on an end face of the saw chipping tool.
In cutting tools, such as circular saw blades and the like especially for separating, a plurality of tooth profiles are known wherein the cutting edge shape or cutting edge arrangement is of special importance with respect to the cut surface and the cut edge quality. Especially in cutting tools with flat tooth geometry, whose separating cutting edges that are provided on the circumference of the tool extend parallel to the axis of rotation and whose greatest width is provided at the separating cutting edges, the impact of the separating cutting edges on the workpiece surface can be compared to a stamping process. By means of this stamping process chipping and cracks result in the entry area of the cutting teeth which must be removed by post processing of the workpiece. In order to reduce the stamping effect of the cutting teeth, it is known to provide the separating cutting edges with lateral bevels. The lateral bevels are designed to lead to the chipping being located within the width of the tooth by reducing the stamping effect. However, increased requirements with regard to the quality of the surface cannot be fulfilled with this measure.
For improving the cut edge quality it is also known to arrange successively cutting teeth with different tooth profiles. In this connection, adjacent to a raker a cutting tooth is arranged which ensures a high surface quality by means of a comparatively reduced material removal. It is also known to arrange together several identical cutting teeth which have arranged adjacent thereto a group of cutting teeth with a different profile shape. Circular saw blades of this type are referred to as circular saw blades with clustered teeth.
DE 35 41 077 A1 discloses a disk-shaped cutting tool with teeth arranged on the outer circumference and having each a cutting edge wherein the cutting edge is formed by a first cutting portion arranged parallel to the rotational axis of the tool and located on the cutting tip and an adjoining lateral cutting part extending in a plane perpendicular to the rotational axis. In the known cutting tool the transition of the cutting edge from the tooth tip to the location of the lateral cutting edges at the widest part of the tool is curved and has a tangential transition into this widest location of the tool. This measure is designed to achieve that the edge finishing cut of the tool to be processed is formed by a flat portion which has a continuous transition into a relatively long cutting edge part producing the workpiece edge. This is designed to reduce loading of the separating cutting edge on the circumference of the tool in the transitional areas to the laterally positioned auxiliary cutting edges as a result of cutting shock so that chipping of the workpiece is prevented. A disadvantage of this solution is that the arc-shaped contour of the lateral cutting edges can produce optimal results with the respective contour curve only for certain workpiece conditions. The arc-shaped cutting edge contours moreover can be produced only in a complicated fashion with the grinding wheels of a corresponding contour, respectively, on machine tools with a correspondingly efficient control.
A cutting blade with arc-shaped convexly formed saw tooth flank is also described in EP 0 691 170 A1. The transition between cutting edge of the cutting tooth and the arc-shaped convex saw tooth flank is designed to be formed in the known saw blade such that the spacing between the center of the saw tooth flank, which corresponds to the greatest tool width, and the symmetry plane of the saw tooth is greater than the spacing between the transition and the symmetry plane. When operating this saw blade, the chip width is however reduced during the cutting process and in the exit area is close to zero. In essence, the cutting edge upon penetrating the workpiece quickly has only a scraping and frictional effect. The scraping requires a substantially higher power output for driving the saw blade so that the range of application of this known circular saw blade is limited to machine tools with a high drive output or to the separation of very thin plates. Moreover, it is to be taken into consideration that there are a plurality of materials which contain greatly abrasive particles. These abrasive particles have an especially negative effect in the phase of scraping with the known circular saw blade and lead to a rounding of the cutting edges already after a very short period of time so that the cutting tool quickly becomes unusable.
DE 297 07 665 U1 discloses a saw tool for sawing wood and metals coated with plastic wherein the cut surface is produced in a similar way as with the cutting tool according to DE 35 41 077 A1 by a draw cut. The known saw tool is a so-called alternating tooth circular saw blade with paired teeth being pointed on one side and arranged successively. The respective second shape is a mirror-symmetrical shape of the first tooth. Since with this crossed tooth arrangement only the longer cutting edge, i.e., every other sawtooth, generates the cut surface quality, a high number of cutting teeth is required.
The present invention has the object to further develop the cutting tool of the aforementioned kind such that a separation and/or formatting of sheet material with cut edges free of tearing and with smooth cut surfaces is made possible while at the same time the required power output of the cutting tool should be as minimal as possible.
In accordance with the present invention, the object is solved in that the main cutting edges in the formatting area are arranged radially separately from the separating cutting edges in the front-cutting area by means of a transition area on the cutting tooth, wherein the transition cutting edges of the transition area adjoin the cutting edges at an angle extending toward the radial center axis of the tool profile.
According to the invention, the separating cutting edges in the front-cutting area positioned radially outwardly on the circumference of the tool are arranged radially separated from farther inwardly positioned main cutting edges in the formatting area, wherein the main cutting edges determine the cutting width. Between the front-cutting area and the formatting area a radial transition area is provided on each one of the cutting teeth, wherein the transition cutting edges of the transition area adjoin the separating cutting edges and are angled relative to the separating cutting edges toward the radial center axis of the tool profile. When operating the cutting tool according to the invention, the transition area between the front-cutting area and the formatting area interrupts the chip formation of the separating cutting edges. The radially farther inwardly positioned main cutting edges thus enter with time delay the workpiece and produced a cut surface of high-quality and a cut edge free of tearing. The separating cutting edges in the front-cutting area separate the workpiece surface and carry out the separating cut. The transition area of the cutting tooth improves moreover the guiding of the separating cutting edges.
The transition cutting edges are positioned at such an angle relative to the central axis and to the separating cutting edges that the chip formation in the separating cutting edges is interrupted. In this context, the transition cutting edges are arranged expediently approximately parallel to the center axis of the tooth profile.
The main cutting edges in the formatting area of the cutting tooth adjoin advantageously the transition cutting edges at an obtuse angle. In this connection, a polygonal profile of the cutting tooth in the front cutting area that is symmetrical with respect to the central axis has been found to be advantageous.